A minor interplanetary shock wave hit Earth on May 26th at approximately 22:00 UT. The CME-like disturbance was unexpected. It caused the density of the solar wind around Earth to abruptly quadruple, while the interplanetary magnetic field doubled in strength. Minor geomagnetic storms are possible on May 27th as our planet passes through the shock wave's wake.
When a stream of solar wind hits Earth's magnetic field, magnetometers around the Arctic Circle normally go a bit haywire, with their needles swinging chaotically as the buffeting ensues. Rob Stammes of the Polarlightcenter, a magnetic observatory in Norway, sees such disordered behavior all the time. But on Nov. 18th something quite different happened. The solar wind produced a pure sine wave:
"A very stable ~15 second magnetic oscillation appeared in my recordings, and lasted for several hours," he says. "The magnetic field was swinging back and forth by 0.06 degrees, peak to peak."
Imagine blowing across a piece of paper, making it flutter with your breath. The solar wind can have a similar effect Earth's magnetic field. The waves Stammes recorded are essentially flutters propagating down the flanks of our planet's magnetosphere excited by the breath of the sun. Researchers call them "pulsations continuous" -- or "Pc" for short..
"A sensitive magnetometer is required to record these waves," says Stammes. "I use a mechanical magnetometer with bar magnets suspended from a special wire. LEDs and light detectors in an isolated dark box record the motion of the magnets, while vanes in oil damp out non-magnetic interference."
Pc waves are classified into 5 types depending on their period. The Nov. 18th waves fall into category Pc3. Researchers have found that Pc3 waves sometimes flow around Earth's magnetic field and cause a "tearing instability" in our planet's magnetic tail. This, in turn, sets the stage for an explosion as magnetic fields in the tail reconnect.
A quartet of NASA spacecraft recently flew through just such an explosion. Last week, researchers from the University of New Hampshire reported that four Magnetospheric Multiscale (MMS) spacecraft spent several seconds inside a magnetic reconnection event as they were orbiting through Earth's magnetic tail. Sensors on the spacecraft recorded jets of high energy particles emerging from the blast site. One jet was aimed squarely at Earth and probably sparked auroras when it hit the upper atmosphere.
Stammes has recorded many Pc waves in the past, "but this is the first time I have detected category Pc3," he says. "This was a very rare episode indeed."
Last weekend, Nov. 10th, a stream of fast-moving solar wind hit Earth's magnetic field, igniting a ring of auroras around the South Pole. Minoru Yoneto saw the red-purple glow all the way from Queenstown, New Zealand:
"We were lucky to catch another Southern Lights display during my stargazing tour," says Yoneta. "Our guests were excited to photograph them using their own cameras."
Queenstown is at 45 degrees south latitude--a considerable distance from the South Pole. That's why the auroras looked red. Auroras circling the South Pole must reach very high above Earth's surface to be visible half a hemisphere away. At altitudes greater than ~200 km, auroras turn red. The ruby glow occurs when high energy particles from space hit oxygen atoms at the top of the atmosphere. Ionized molecular nitrogen adds a dash of purple to the high-altitude palette.
More red Southern Lights are possible on Nov. 18th or 19th when a new stream of solar wind is expected to arrive. The gaseous material is flowing from a relatively small hole in the sun's atmosphere. Queenstown stargazers, charge your cameras!
The Parker Solar Probe has just radioed NASA with good news. The spacecraft survived its close approach to the sun on Nov. 5th. Because the sun is a giant natural source of broadband radio noise, Parker cannot transmit complicated data streams through the interference. Images and data won't arrive until early December when the probe has reached a sufficient distance from the sun again. For now, mission controllers are happy to have received a simple beacon saying the spacecraft is okay.
First Perihelion: Into the Unknown - Parker Solar Probe
JHU Applied Physics Laboratory
Published on Nov 2, 2018
Earlier this week, Parker screamed around the sun at 213,200 mph only 15 million miles from the stellar surface--shattering old records for both speed and distance. Intense sunlight raised the temperature of the probe's heat shield to about 820 degrees Fahrenheit. All the while, instruments and systems behind the shield kept cool in the mid-80s F.
Mission controllers at the Johns Hopkins University Applied Physics Lab received the status beacon at 4:46 p.m. EST on Nov. 7, 2018. It indicated, simply, "A" — the best of all four possible status signals, meaning that the probe is operating well with all instruments running and collecting science data and, if there were any minor issues, they were resolved autonomously by the spacecraft. Stay tuned for "first light" science results about one month from now.
NASA's Parker Solar Probe is now closer to the sun than any other spacecraft in history, shattering the previous record of 26.6 million miles set by the Helios 2 spacecraft in 1976. The probe is now well inside the orbit of Mercury."It's a proud moment for our team," says Project Manager Andy Driesman of the Johns Hopkins Applied Physics Laboratory.
Count to 3. Parker just broke the record again. The spacecraft is accelerating sunward for the mission's first perihelion on Nov. 5th. At closest approach, the solar disk will seem 6 times wider than it does on Earth as the probe is hit by "brutal heat and radiation" (NASA's words). Parker's carbon-composite heat shield is expected to heat up to a sizzling 2000 deg. F.
Parker's prime mission is to investigate the origin of the solar wind--a project best done uncomfortably close to the star. Parker will trace the solar wind back to its source and find out how it escapes the sun's gravity and magnetic confinement.
Russell Howard of the Naval Research Laboratory expects to learn a lot from this encounter. "We might detect magnetic islands in the solar wind, which have been theoretically predicted. And if a CME (solar explosion) happens or a comet passes through the sun's atmosphere while we are so nearby, it could be spectacular."
Howard is the principal investigator for WISPR, the probe's wide-field camera system. WISPR can actually see the solar wind, allowing it to image clouds and shock waves as they approach and pass the spacecraft. Other sensors on the spacecraft will sample the structures that WISPR sees, making measurements of particles and fields that researchers can use to test competing theories.
"We lose communication with the spacecraft during the perihelion period which begins next week," notes Howard. "This is because there isn't sufficient power to drive both the instruments and the transmitter. The first dump of data will occur in early December." Stay tuned for that.
Parker will plunge toward the sun 24 more times in the next 8 years, breaking many records en route. Here's the timeline.
On Oct. 26th, Venus will pass almost directly between Earth and the sun--an event astronomers call "inferior solar conjunction." As Venus approaches the sun, the planet is turning its night side toward Earth, reducing its luminous glow to a thin sliver. Shahrin Ahmad of Kuala Lumpur, Malaysia, took this picture on Oct. 20th:
"I took this picture in broad daylight," says Ahmad. "Venus was really big in the eyepiece of my telescope--almost a full arcminute in diameter. And the crescent shape easily visible in the 8x50 finder scope."
In the days ahead, the crescent of Venus will become increasingly thin and circular. The horns of the crescent might actually touch when the Venus-sun angle is least (~6 degrees) on Oct. 26th. This is arguably the most beautiful time to observe Venus, but also the most perilous. The glare of the nearby sun magnified by a telescope can damage the eyes of anyone looking through the eyepiece.
Anthony J. Cook of the Griffith Observatory has some advice for observers: "I have observed Venus at conjunction, but only from within the shadow of a building, or by adding a mask to the front end of the telescope to fully shadow the optics from direct sunlight. This is tricky with a refractor or a catadioptric, because the optics start at the front end of the tube. Here at Griffith Observatory, I rotate the telescope dome to make sure the lens of the telescope is shaded from direct sunlight, even through it means that the lens will be partially blocked when aimed at Venus. With our Newtonian telescope, I add a curved cardboard mask at the front end of the tube to shadow the primary mirror."
For the rest of this week Venus can still be observed without elaborate precautions in deep twilight after sunset. Every evening the crescent grows and narrows. Scan the realtime photo gallery for updates.
The sun is entering a deep Solar Minimum, and Earth's upper atmosphere is responding. Data from NASA's TIMED satellite show that the thermosphere (the uppermost layer of air around our planet) is cooling and shrinking, literally decreasing the radius of the atmosphere. If current trends continue, the thermosphere could set a Space Age record for cold in the months ahead: Full story.
The Moon is about to take a bite out of the sun. On Saturday, August 11th, there will be a partial solar eclipse visible from locations around the Arctic Circle and across much of Asia. During the 3+ hour event, as much as 73% of the solar disk will be covered. Selected cities in the eclipse zone include Moscow (2.1% coverage), Oslo (4.8%), Raykjavik (20%), Tromso (29%), and Seoul (35%). www.spaceweather.com
An interplanetary shock wave hit Earth's magnetic field on April 19th around 23:50 UT. When the disturbance arrived, the density of solar wind flowing around our planet abruptly quadrupled and a crack opened in Earth's magnetic field. The resulting G2-class geomagnetic storm sparked unusual "electric blue" auroras.
"I've been flying airplanes for 20 years and photographing aurora for 10 years, but I've never seen anything like this before" reports pilot Matt Melnyk, who photographed the display from 39,000 feet. "Electric blue auroras!" he says. "This was while on a red eye flight from Edmonton to Toronto around 4 am over northern Manitoba. Unbelievable sky. I was able to grab some hasty shots with a cell phone."
Auroras are usually green--a sign of oxygen. Rare blue auroras are caused by nitrogen molecules. Energetic particles striking N2+ at the upper limits of Earth's atmosphere can produce an azure glow during intense geomagnetic storms.
What is an interplanetary shock wave? It is a supersonic disturbance in the gaseous material of the solar wind. These waves are usually delivered by coronal mass ejections (CMEs). Indeed, this one might have been a minor CME that left the sun unrecognized earlier this week.
Alternately, it might have been an unusually sharp co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. They contain plasma density gradients and magnetic fields that often do a good job sparking auroras.
See also: 'Strong New Moon, Solar Activity and Gateways Ahead' by Sandra Walter, Wayshower, Ascension Guide and Gatekeeper
A strong geomagnetic storm was brewing in the skies above Alberta, Canada, on Sept. 27th when photographer Alan Dyer looked up and saw a ribbon of purple light arcing cross the sky. It was the mysterious aurora known as "Steve":
"The Steve arc appeared for only about 20 minutes, starting at 10:45 pm MDT, during a lull in the main display," says Dyer, who captured the arc in a 6-shot, 360o panorama.For many years, northern sky watchers have reported this luminous form occasionally dancing among regular auroras. It was widely called a "proton arc" until researchers pointed out that protons probably had nothing to do with it. So members of the Alberta Aurora Chasers group gave it a new name: "Steve."
"We seem to be ideally located in the Canadian Prairies for sighting Steve, as we often get the main aurora to our north, placing Steve overhead or to our south," notes Dyer.
No one fully understands the underlying physics of the purple ribbon. One of the European Space Agency's Swarm satellites flew straight through Steve during a previous apparition. Data revealed a relatively hot river of gas, about 25 km wide, flowing rapidly through Earth's outer atmosphere. "Steve seems to be a thermal emission from hot flowing gas rather than from precipitating electrons," says Dyer, "but his origin and nature are still mysterious." www.spaceweather.com
GEOMAGNETIC STORM PREDICTED: NOAA forecasters say there is a 75% chance of moderately strong (G2-class) geomagnetic storms on Sept. 13th. That's when a CME hurled into space by a powerful X8-class solar flare on 10 September will likely deliver a glancing blow to Earth's magnetic field. The impact of the CME could be enhanced by a fast-moving solar wind stream, expected to arrive at about the same time. If the G2-storm materializes, auroras in the USA could appear as low as New York to Wisconsin to Washington state.
SOLAR RADIATION STORM AND GROUND LEVEL EVENT: On Sept. 10th, departing sunspot AR2673 erupted, producing a powerful X8-class solar flare. The explosion propelled a CME into space and accelerated a swarm of energetic protons toward Earth. Both are visible in this coronagraph movie from the Solar and Heliospheric Observatory (SOHO):
(go to http://spaceweather.com/ to watch animation)
The many specks in this movie are not stars--they are solar protons striking SOHO's digital camera. Almost two days later these protons are still streaming past our planet, causing a moderately strong (S2-class) solar radiation storm. The latest data from SOHO show an ongoing blizzard of digital "snow" in coronagraph images:
What made this flare so 'radioactive'? It has to do with the location of AR2673 at the time of the explosion. The sun's western limb is magnetically well-connected to Earth. Look at this diagram. Magnetic fields spiraling back from the blast site led directly to our planet, funneling these energetic protons Earthward.
Normally, solar radiation storms are held at bay by our planet's magnetic field and upper atmosphere. On Sept.10th, however, there was a "ground level event" (GLE). Neutron monitors in the Arctic, Antarctic, and several other high latitude locations detected a surge of particles reaching all the way down to Earth's surface:
The Bartol Research Institute's South Pole Neutron Monitor detected a GLE on Sept. 10th.
"In historical terms, this was a relatively small ground level event-- only about one thousandth as strong as the event of 23 Feb 1956, which is the largest measured," says Clive Dyer, a Visiting Professor at the University of Surrey Space Centre.
However, that does not mean the Sept.10th GLE was negligible. Dyer says that "passengers flying on high-latitude routes at 40,000 feet could have absorbed an extra 10 microSieverts of radiation. During the first hour of the GLE, the dose rate inside the aircraft during such a flight would have approximately doubled."
He also notes that the GLE could have caused minor upsets of onboard electronics and avionics, although nothing on the scale of the epic 1956 GLE, "which would be very challenging to modern systems."
"Since measurements began around 1942 there have now been 73 events detected by ground level radiation monitors," Dyer adds. "The Sept.10, 2017, event is far from the strongest, but it is of special interest because it demonstrates the need for continual vigilance even during Solar Minimum." www.spaceweather.com
On Sept. 6th at 12.02 UT, sunspot AR2673 unleashed a major X9.3-class solar flare--the strongest solar flare in more than a decade. X-rays and UV radiation from the blast ionized the top of Earth's atmosphere, causing a strong shortwave radio blackout over Europe, Africa and the Atlantic Ocean (blackout map). The explosion also produced a CME, shown here in a movie from NASA's STEREO-A spacecraft. (The fast moving star-like object in the STEREO-A movie is the planet Mercury.) NOAA analysts are still modeling the trajectory of the CME to determine whether or not it is Earth-directed.
Many readers are asking about the historic context of this event. How epic is it? Answer: This is a decade-class flare. A list of the most powerful solar flares recorded since 1976 ranks today's flare at #14, tied with a similar explosion in 1990. Compared to the iconic Carrington Event of 1859, or even the more recent Halloween storms of 2003, this event is relatively mild. Modern power grids, telecommunications, and other sun sensitive technologies should weather the storm with little difficulty.
On the other hand, sky watchers could see some fantastic auroras before the week is over. And ham radio operators will surely be noticing strange propagation effects as the sun exerts its influence on our planet's ionosphere.Stay tuned for updates.
Above: The extreme UV flash from today's X9-class flare. Credit: Solar Dynamics Observatory
The source of today's major flare is huge sunspot AR2673, shown here in a Sept. 5th photo taken by amateur astronomer Philippe Tosi of Nîmes, France:
How big is AR2673? An image of Earth has been inserted for scale. The largest of AR2673's dark cores are as wide as our entire planet, and they are surrounded by dozens of smaller cores as big as continents. Amateur astronomers with safely-filtered solar telescopes will have no trouble seeing this behemoth. Overarching the complex collection of spots is a tangled magnetic canopy that harbors energy for strong solar flares. Stay tuned for more explosions...
Only a few weeks ago, it seemed that the sun would be quiet and featureless when the Moon eclipsed it on Aug. 21st. Solar Minimum was in full swing. This weekend, however, the sun is welcoming the eclipse with a burst of renewed activity. "As the Moon approaches the sun, our nearest star is extending a friendly hand towards it," says Dave Eagle who sends this picture from Higham Ferrers, England:
"There is a huge prominence on the sun's eastern limb. If you are in the total eclipse path set your clock to greet this awesome spectacle on Monday," he says.
And that's just for starters. In addition, a remarkably-long sunspot group is sprawling across the solar disk. AR2671 stretches 140,000 miles from end to end, almost twice as wide as the planet Jupiter. Bill Hrudey sends this picture of the behemoth from the Cayman Islands:
Amateur astronomers watching the eclipse through safe solar telescopes will have no trouble seeing the rugged edge of the Moon cut across this impressive sunspot, eclipsing one dark core after another. If we're really lucky, the sunspot will explode. AR2671 has a 'beta-gamma' magnetic field that harbors energy for M-class solar flares. Free: Solar Flare Alerts
On Aug. 21, 2017, every square inch of the USA will experience a solar eclipse. In most places, the eclipse will be partial - that is, the Moon will cross the sun off-center, leaving a crescent shaped portion of the solar disk exposed. Is it really worth the trip to the path of totality when you can stay home and see the partial eclipse? Pulitzer prize winner Annie Dillard, who witnessed both types of eclipses in 1979, compared them as follows:
"A partial eclipse is very interesting. It bears almost no relation to a total eclipse. Seeing a partial eclipse bears the same relation to seeing a total eclipse as kissing a man does to marrying him, or as flying in an airplane does to falling out of an airplane."
Indeed, during the minutes of totality, the whole world changes. Saying that day turns into night barely scratches the surface of it. The shadow of the Moon lances down to Earth from a quarter million miles away. On one end is you; on the other end is a million square miles of dusty lunar terrain. You're connected, and you can feel the cold.
Image Credit & Copyright: Tunç Tezel (TWAN), Alkim Ün
Darkness inside the path of totality has an alien quality. Because the shadow is only 70 miles wide, you can see daylight at the edges even while you stand in the dark core. This distant scattered light produces a slight reddish glow and unusual shadow effects. Many birds stop singing, daytime flower blossoms begin to close as if for the night, and bees return to their hives.
"What you see in an eclipse is entirely different from what you know," says Dillard, whose brilliant essay "Total Eclipse" is a must-read for anyone deciding whether to stay home ... or have their minds blown.
What do Christmas Eve, Christmas, and Boxing Day 2016 have in common? They were days without sunspots. Throughout the holiday weekend, the face of the sun was completely blank, and the sun itself looked like a big orange Christmas ornament:
Including Dec. 24th, 25th and 26th, 2016 has had 31 'spotless days'--a whole month's worth. We haven't had this many blank suns in a single year since 2010 (51 days). This is a sign that the sunspot cycle is crashing toward a new Solar Minimum.
There are many misconceptions about Solar Minimum. One holds that auroras vanish when sunspots disappear. Christmas Day 2016 was proof that the opposite is true. Without a hint of a sunspot on the solar disk, intense auroras raged around the Arctic Circle on Dec. 25th. What caused the luminous outburst? An enormous hole in the sun's atmosphere directed a stream of solar wind toward Earth, sparking a week-long display that is still underway. Such atmospheric holes are common during Solar Minimum, which is a fine time to see Arctic auroras.
Many people think space weather becomes dull or stops altogether during Solar Minimum. In fact, space weather changes in interesting ways. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth; galactic cosmic rays penetrate our atmosphere with relative ease. Yes, Solar Minimum is coming ... but it won't be dull.
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